Cosmological model with macroscopic spin fluid

Szydłowski, Marek; Krawiec, Adam

doi:10.1103/physrevd.70.043510

Cited by 26 publications

(40 citation statements)

References 23 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Then, unlike in [156], although the spin sector in EC framework plays an important role in the early stages of the universe with a repulsive gravitational effect, at late times the cosmological constant or dark energy term proposed by Padmanabhan is required again to achieve the holographic equipartition in this model. This fact is in agreement with the result obtained in [131] where the luminosity distance is implemented to test the models using the supernovae type Ia observations. There, the authors showed that although a cosmological model with a spin fluid is admissible, the cosmological constant is still required to explain the accelerating expansion of the universe.…”

Section: Emergence Of Spacetime In Einstein-cartan Theorysupporting

confidence: 80%

“…Similar to the other alternative theories of gravity, the cosmological solutions of the EC theory possessing the spin matter source and their influence on the structure and dynamics of the universe are extensively investigated. These studies include the effects of torsion and spinning matter in a cosmological setup and its possible role to solve the singularity problems, pre-Friedmann stages of evolution, inflationary expansion, the late time accelerated expansion of the universe, rotation of the universe, gravitational collapse, and so on [128][129][130][131][132][133][134][135][136][137][138][139][140].…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Emergent cosmos in Einstein–Cartan theory

et al. 2018

View full text Add to dashboard Cite

Based on Padmanabhan's proposal, the accelerated expansion of the universe can be driven by the difference between the surface and bulk degrees of freedom in a region of space, described by the relation dV /dt = N sur − N bulk where N sur and N bulk = −N em + N de are the degrees of freedom assigned to the surface area and the matter-energy content inside the bulk such that the indices "em" and "de" represent energy-momentum and dark energy, respectively. In the present work, the dynamical effect of the Weyssenhoff perfect fluid with intrinsic spin and its corresponding spin degrees of freedom in the framework of Einstein-Cartan (EC) theory are investigated. Based on the modification of Friedmann equations due to the spin-spin interactions, a correction term for Padmanabhan's original relation dV /dt = N sur +N em −N de including the number of degrees of freedom related with these spin interactions is obtained through the modification in N bulk term as N bulk = −N em + N spin + N de leading to dV /dt = N sur + N em − N spin − N de in which N spin is the corresponding degrees of freedom related with the intrinsic spin of the matter content of the universe. Moreover, the validity of the unified first law and the generalized second law of thermodynamics for the Einstein-Cartan cosmos are investigated. Finally, by considering the covariant entropy conjecture and the bound resulting from the emergent scenario, a total entropy bound is obtained. Using this bound, it is shown that the for the universe as an expanding thermodynamical system, the total effective Komar energy never exceeds the square of the expansion rate with a factor of 3 4π .

show abstract

Section: Emergence Of Spacetime In Einstein-cartan Theorysupporting

confidence: 80%

Section: Introductionmentioning

confidence: 99%

Emergent cosmos in Einstein–Cartan theory

et al. 2018

View full text Add to dashboard Cite

show abstract

“…In order to have better understanding of the new terms with θJ 2 in (3.26), we can consider the simplified cosmological model with vanishing ρ 0 and p 0 . It is easy to solve the Friedmann equation, H 2 = (8πG/3) ρ and obtain the corresponding rule for the expansion of the universe, 27) which, again, is different from the laws of expansion for free radiation (with a ∼ t 1/2 ) and dust (with a ∼ t 2/3 ). The results (3.23) and (3.27) do not depend on the value of BI parameter.…”

Section: Massless Casementioning

confidence: 99%

“…Following the Lagrangian formalism for this exotic spin fluid [22][23][24], one can see that the contribution from such fluid always produces a traceless torsion [25] (for the extensive discussion of the theories with spin fluid in cosmology, see also Refs. [26][27][28][29][30][31][32]). In this case the trace of the torsion tensor T µ = T α µα has smaller physical meaning and its presence is completely due to the nonminimal procedure [14,15].…”

Section: Introductionmentioning

confidence: 99%

Dirac fields, torsion and Barbero-Immirzi parameter in cosmology

Berredo-Peixoto

Freidel

Shapiro

et al. 2012

J. Cosmol. Astropart. Phys.

View full text Add to dashboard Cite

Abstract. We consider cosmological solution for Einstein gravity with massive fermions with a four-fermion coupling, which emerges from the Holst action and is related to the BarberoImmirzi (BI) parameter. This gravitational action is an important object of investigation in a non-perturbative formalism of quantum gravity. We study the equation of motion for the Dirac field within the standard Friedman-Robertson-Walker (FRW) metric. Finally, we show the theory with BI parameter and minimally coupling Dirac field, in the zero mass limit, is equivalent to an additional term which looks like a perfect fluid with the equation of state p = wρ, with w = 1 which is independent of the BI parameter. The existence of mass imposes a variable w, which creates either an inflationary phase with w = −1, or assumes an ultra hard equation of states w = 1 for very early universe. Both phases relax to a pressure less fluid w = 0 for late universe (corresponding to the limit m → ∞).

show abstract

“…Because this model unifies both the RSB model with vanishing dark radiation and the model with spinning fluid [39] we include this model to the class of models which are based on the modified FRW equation. Because the RSB and MAG models without the cosmological constant do not fit well the SNIa data [10,38,40] we also analyze the MAG and RSB models with the non-vanishing Λ term.…”

Section: Introductionmentioning

confidence: 99%

Which cosmological model—with dark energy or modified FRW dynamics?

Szydłowski¹,

Godlowski²

2006

Physics Letters B

Self Cite

View full text Add to dashboard Cite

Abstract. Recent measurements of distant type Ia supernovae (SNIa) as well as other observations indicate that our universe is in accelerating phase of expansion. In principle there are two alternative explanation for such an acceleration. While in the first approach an unknown form of energy violating the strong energy condition is postulated, in second one some modification of FRW dynamics is postulated. The both approaches are in well agreement with present day observations which is the manifestation of the degeneracy problem appearing in observational cosmology. We use the Akaike (AIC) and Bayesian (BIC) information criteria of model selection to overcome this degeneracy and to determine a model with such a set of parameters which gives the most preferred fit to the SNIa data. We consider five representative evolutional scenarios in each of groups. Among dark energy proposal the ΛCDM model, CDM model with phantom field, CDM model with topological defect, model with Chaplygin gas, and the model with the linear dynamical equation of state parameter. As an alternative prototype scenarios we consider: brane world Dvali Gabadadze Porrati scenario, brane models in Randall-Sundrum scenario, Cardassian models with dust matter and radiation, bouncing model with the cosmological constant and metricaffine gravity (MAG) inspired cosmological models. Applying the model selection criteria we show that both AIC and BIC indicates that additional contribution arises from nonstandard FRW dynamics are not necessary to explain SNIa. Adopting the model selection information criteria we show that the AIC indicates the flat phantom model while BIC indicates both flat phantom and flat ΛCDM models.

show abstract

Cosmological model with macroscopic spin fluid

Cited by 26 publications

References 23 publications

Emergent cosmos in Einstein–Cartan theory

Emergent cosmos in Einstein–Cartan theory

Dirac fields, torsion and Barbero-Immirzi parameter in cosmology

Which cosmological model—with dark energy or modified FRW dynamics?

Contact Info

Product

Resources

About